Technical Field of the Invention
The present invention relates to an apparatus for moulding food products of mouldable food materials.
More specifically, the invention concerns such an apparatus as has a moulding compartment for the mouldable food material, a feeding device for feeding the mouldable food material to the moulding compartment, a moulding plate with a mould cavity, said moulding plate being movable between a feeding position, in which the mould cavity communicates with the moulding compartment via a moulding opening, and an ejection position, in which the mould cavity is open towards a base, a plunger assembly for filling the mould cavity with the food material from the moulding compartment via the moulding opening, and a means for ejecting a food product moulded in the mould cavity from the moulding plate in the ejection position.
A moulding apparatus of this kind comprises a plurality of movable parts, the movements of which are to be coordinated and may need adjustment relative to each other. For the driving of the various parts, the prior-art technique utilises an electric motor, which via cam discs, cranks and the like controls the movement pattern of the various parts. To achieve the desired movements, a hydraulic system can also be used to supplement the electric motor or, alternatively, to replace the same. Examples of known moulding apparatus are to be found in, for instance, U.S. Pat. No. 4,975,039 and GB Patent 1,219,452.
In consequence of the many movable parts and the necessary coordination of the various movements, the driving of the prior-art moulding apparatus is complicated. The prior-art moulding apparatus are also not very suited for adaptation of the driving to the different products based on different mouldable food materials which each have specific properties.
An object of the present invention therefore is to simplify the driving of a moulding apparatus of the type described by way of introduction, such that both the coordination of the different movements and the appearance of each individual movement can be controlled and changed in a quick and reliable manner. As a result, it should also be possible to give the mouldable food product a very kind treatment, such that the quality of the moulded food product becomes high.
This object is achieved by the moulding apparatus being given the distinguishing features that are evident from appended claim 1. Preferred embodiments of the inventive moulding apparatus appear from the dependent claims.
According to the invention, use is thus made of a common, programmable control unit for predetermining the movements of the feeding device, the plunger assembly and the moulding plate as a function of time in the form of separate, periodical movement patterns, which have the same predeterminable period and a predeterminable time relationship between each other. Moreover use is made of a separate drive unit for each of the feeding device, the plunger assembly and the moulding plate for controlling the movement of each of them into continuous agreement with the respective one of movement patterns predetermined by the common, programmable control unit.
The separate drive unit for the plunger assembly and the moulding plate, respectively, may comprise a servo-operated motor capable of taking positions in accordance with the predetermined movement pattern, which comprises both the extent of the movement, i.e. the length and position of the path of movement, and the speeds of the movement in each period, i.e. residence times in points at zero speed and speed variations between these points.
The common, programmable control unit comprises a programmable logic circuit of a known kind and output circuits which are also of a known kind for transmitting driving signals of a suitable form for the various drive units.
The feeding device has suitably at least two feed screws for feeding the mouldable food material to the moulding compartment from a storage container. The separate drive unit for the feeding device may then comprise a servo-operated motor capable of rotating the feed screws according to the predetermined movement pattern, which in this case comprises the variation of the rotational speed during each period.
The common, programmable control unit is in the first place programmable in respect of the length of the period, but it is suitably also programmable in respect of length and position of the movement of the moulding plate, especially the position of the feeding position, the residence time of the moulding plate in the feeding position and its residence time in the ejection position as well as the velocity profile at least for the movement of the moulding plate from the feeding position to the ejection position.
Moreover, the common, programmable control unit is preferably programmable in respect of the synchronisation of the movement pattern of the plunger assembly relative to the movement pattern of the moulding plate. It is also in this case very important for the length and the position of the movement of the plunger assembly to be programmable, as are the residence times of the plunger assembly in inoperative positions and the profiles or variation of its speeds between these positions.
Further preferred programming possibilities of the common, programmable unit will appear from the following specification of a preferred embodiment.
It will be appreciated that the inventive moulding apparatus for food products has a number of advantages compared with the prior-art moulding apparatus. Thus, the programmable control unit may comprise a plurality of programs for a food product each, such that the apparatus can very easily be adjusted for the manufacture of a food product of current interest.
By the program control and the separate drive units, corrections can also be easily carried out in consideration of minor deviations between the properties which a stored program assumes for a mouldable food material and the properties of a particular volume of this food material.
The use of separate drive units also implies that a change of the movement pattern for one drive unit does not necessarily affect the movement pattern for another drive unit. However, the synchronisation between the different drive units can easily be changed by using the program control and the separate drive units.
According to the food product, the time for each period or each cycle that the moulding apparatus performs can thus be varied very easily to a value which is optimal for each individual food product and each run.
Each individual movement pattern can, of course, be changed from one run to the next, for instance, the period can be changed, i.e. the number of produced products per unit of time, without changing the movement pattern in that part which concerns the filling of the mould cavity of the moulding plate. It is also possible to vary the movement pattern from cycle to cycle, i.e. during a run.